Spin-Induced Nonlinear Scalarization of Kerr Black Holes in Einstein-scalar-Gauss-Bonnet Gravity

Abstract

We investigate spin-induced scalarization of Kerr black holes in an Einstein-scalar-Gauss-Bonnet (EsGB) model that does not admit a linear tachyonic instability of the scalar-free solution. The scalarization mechanism is therefore genuinely nonlinear. We first analyze the decoupled scalar dynamics on fixed Kerr backgrounds and show that sufficiently rapid rotation modifies the Gauss-Bonnet invariant such that a negative near-horizon region develops near the poles. This region provides a geometric trapping mechanism for nonlinear scalar growth, which becomes effective above a threshold spin $\chi =0.5$. We then construct stationary scalarized black hole solutions with full backreaction and determine their domain of existence. We find that the solutions occupy a finite low-mass high-spin wedge in the spin-mass plane. This is in contrast to spin-induced spontaneous scalarization, where the scalarized solutions form a narrow band. In this wedge, toward the high-spin end, the scalar hair becomes stronger, and the solutions approach a near-extremal regime, while toward the low-spin boundary, the scalar field is strongly suppressed and approaches a weak-hair limit as $\chi \to 0.5$.

References in corpus (13)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Instability of the massive Klein-Gordon field on the Kerr spacetime
• Spontaneously scalarised Kerr black holes
• Quasinormal modes of scalarized black holes in the Einstein-Maxwell-Scalar theory
• Gauss-Bonnet black holes with a massive scalar field
• Spontaneously scalarized black holes in dynamical Chern-Simons gravity: dynamics and equilibrium solutions
• A new approach and code for spinning black holes in modified gravity
• Spontaneous nonlinear scalarization of Kerr black holes
• Nonlinearly scalarized rotating black holes in Einstein-scalar-Gauss-Bonnet theory
• Rotating scalarized black holes: the role of the coupling
• Existence of nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory with polynomial couplings
• Massive scalar clouds and black hole spacetimes in Gauss-Bonnet gravity